Assay devices are utilized in a wide variety of fields, most notably medical diagnostics, to test for materials of interest, such as antigens from infection causing organisms. In the medical field, given the already large number of known infections, and the ever growing number of new infections, assay technology has become increasingly important.
For example, streptococci is an organism that can cause illnesses such as tonsillitis, pharyngitis, and scarlet fever. If left untreated, a strep infection can lead to numerous complications, such as rheumatic fever. Therefore, it is important to treat infections as quickly and effectively as possible.
However, before an infection can be treated the infection causing agent must be identified. Confirmation of the presence and identity of infective agents in a patient is best affected by diagnostic procedures that are usually multiple step processes comprising: (1) sampling a bodily fluid, e.g. blood, saliva, urine, etc . . . ; (2) filtering the fluid in order to better isolate any antigens present; (3) contacting the filtered fluid with a detection material that contains bound antibodies reactive with the antigens of interest so that the antigens of interest bind to the antibodies and, therefore, to the detection device; and (4) contacting the detection device with "detector" antibodies that are reactive with the antigens of interest and that also contain bound signal producing systems such as dyes. The antibodies and therefore, the dyes, attach to the bound antigens and, thereby, in the simpliest case, provide a visual marker signifying the presence and identity of the antigens.
The antibodies described in the forestated process are blood serum proteins that are formed by the body as a natural part of its response to the introduction of an antigen. The entire science of immunology is based on antigen-antibody reactions, the most outstanding feature of which is their specificity. Antibodies in the bloodstream usually react only with the antigen used to stimulate their production or with antigens of a similar molecular structure. The specificity of antibodies towards antigens is due not so much to the composition of the molecules as it is to the configuration of the molecules.
In the prior art, multiple devices are necessary to perform the multiple step process of detecting and identifying antigens. In one such example, bodily fluid is drawn into a capillary tube. The bodily fluid is then dropped into a dispensing tube that contains a lysing reagent. A tip containing a sifting filter is then utilized to cover the tube opening. As used in this application, the term "sifting filter" means any material utilized to limit the size or nature of components present in a test fluid sample. The sifting filter, upon inversion of the dispensing tube, allows lysed fluid to pass out of the tube. The dispensing tube is then inverted and a drop of lysed fluid is placed into a well on a reaction stand.
Prior art assays generally comprise: (1) a "reservoir filter," defined herein as any filter that absorbs excess test fluid and increases the capillary action drawing the test fluid through the assay device; (2) a detection zone that is aligned contiguous to the reservoir filter, which comprises a detection zone base material, such as nitrocellulose, and a means for detecting the material of interest, in this case attached homologous antibodies reactive with the antigen of interest; and (3) a backing that supports both the reservoir filter and the detection zone. Optionally, a protective covering, usually plastic, can also be added that is bound to the backing and extends over the reservoir filter and/or the detection material to further bind the materials to the backing.
The prior art assays may be dipped into the lysed fluid so that the fluid enters the assay as close to the terminal point of the detection material as possible. Capillary action then sucks the fluid through the detection zone and into the reservoir filter. The attached antibodies in the detection zone then chemically and/or physically bind the antigens as they pass through the detection zone. Concurrently, or in a subsequent step, detector antibodies that contain bound dyes are contacted with the bound antigens. The antibodies that contain bound dyes attach to the bound antigens and provide a visual color marker that signifies the presence and identify of the antigens.
One problem with the prior art method is that multiple devices (capillary tube, dispensing tube, sifting filter tip, and assay) are necessary, or the process is cumbersome, time consuming and prone to contamination error. The practitioner needs to ensure the sterility and integrity of at least four different devices to avoid contamination.
In addition, there is no mechanism in the prior art assays that controls the test fluid in a manner sufficient to ensure that it only enters the assay at the terminus of the detection zone. This is critical for optimal performance of the system since antigens contained in fluid entering the sides of the detection zone may miss many of the bounded antibodies and, therefore, never be detected. Although hard plastic casings presumably offer a modicum of control over the flow of test fluids and are known for use in assays, these casings are less efficient, bulky and expensive.
In response to long felt needs in the industry, and in an effort to rectify the problems inherent in the prior art devices for detecting and identifying antigens, applicants have designed an improved device for conducting assays.
The device disclosed within this application performs both the sifting filter process and the assay process, thereby cutting time, effort, and the risk of contamination. The inventive device utilizes shrink wrap technology to encase the sifting filter contiguous to the assay test strip. However, the shrink wrap does more than simply serve as a encasing agent. The shrink wrap also directs the test fluid in a manner that ensures that it only enters the assay through the terminus of the sifting filter and, subsequently, the terminus of the detection zone. As stated, this is critical for a working system.
Furthermore, the device disclosed within this application may be identical to any one of several conventional assays but, instead of being encased in a hard plastic, it is encased in shrink wrap.
The phrase "shrink wrap," as used in this application, is defined as a plastic film that reduces in size upon application of heat. Shrink wrap is an ideal encasing material since it is both cheap to produce and easily integrated into mass production assemblies. As a result, the use of shrink wrap to produce an improved assay adds minimal cost to assay production. This cost advantage cannot be overstated. Although assays are universally utilized in the medical industry to test for an already enormous, and ever expanding, number of infections, the large demand for assays is countered by an even larger aversion to increased health care costs. Therefore, any improvement in the assay art that is significantly more expensive is not readily accepted. In contrast, the traditional hard plastic casings are very expensive.
In addition, shrink wrap provides a tighter casing around the assay than can be obtained with the traditional hard plastic casings. As a result, shrink wrap is more effective in directing the test fluid so that it only enters the assay through the terminus of the detection zone.
Finally, unlike the traditional hard plastic casings, shrink wrap provides a very thin casing which makes handling and storage easier.
Although the inventive assay device is primarily geared toward detecting and identifying infection causing antigens in bodily fluids, it should be recognized, and is certainly envisioned, that the assay device is capable of detecting and identifying any material of interest in any biological and/or industrial fluid, as long as the detection zone contains a means of chemically, and/or physically, trapping, and/or tagging, the material of interest. The nature of the means of trapping and/or tagging the material of interest will naturally vary according to the nature of the material of interest and is readily ascertainable by those of ordinary skill in the art. For example, if the material of interest is a DNA, the means of trapping and/or tagging the material of interest is a complementary DNA and, if the material of interest is an PNA (Peptide Nucleic Acid), the means for trapping and/or tagging the material of interest is a complementary PNA. An infinite number of compounds can be detected in biological and/or industrial fluids utilizing the inventive assays, including, but not limited to, analytes, antigens, polynucleotides, oligonucleotides, small molecules, drugs of abuse, therapeutic drugs, carbohydrates, environmental and carcinogenic agents, parasites, bacteria, viruses, and prions.